SQL内部连接:数据库卡住 [英] SQL Inner Join : DB stuck

问题描述

几天前，我张贴了这个问题，但我没有确切说明我想要的. 我再次提出更好的问题: 为了澄清我的问题，我添加了一些新信息:

I postet this question a few days ago but I didn't explain exactly what I want. I ask the question better formulated again: To clarify my problem I added some new information:

我有一个带有MyISAM表的MySQL数据库.两个相关的表是:

I got an MySQL DB with MyISAM tables. The two relevant tables are:

* orders_products: orders_products_id, orders_id, product_id, product_name, product_price, product_name, product_model, final_price, ...
* products: products_id, manufacturers_id, ...

(有关表格的完整信息，请参见屏幕截图产品(屏幕截图)和截图screenshot_products(截图))

(for full information about the tables see screenshot products (Screenshot) and screenshot orders_products (Screenshot))

现在我想要的是:-获取所有订购了Manufacturers_id = 1的产品的订单.此订单产品的产品名称(Manufacturers_id = 1).按订单分组.

Now what I want is this: - Get all Orders who ordered products with manufacturers_id = 1. And the product name of the product of this order (with manufacturers_id = 1). Grouped by orders.

到目前为止，我所做的是:

What I did so far is this:

SELECT
op.orders_id,
p.products_id,
op.products_name,
op.products_price,
op.products_quantity
FROM orders_products op , products p 
INNER JOIN products
ON op.products_id = p.products_id
WHERE p.manufacturers_id = 1 AND
p.orders_id > 10000

p.orders_id> 10000以进行测试以仅获取几个order_id.但是，即使查询有效，它们的查询也需要花费大量时间才能执行.两次sql服务器卡住了.错误在哪里?

p.orders_id > 10000 for testing to get only a few order_id's. But thies query takes much time to get executed if it even works. Two times the sql server stucked. Where is the mistake?

推荐答案

SELECT 
op.orders_id, 
p.products_id, 
op.products_name, 
op.products_price, 
op.products_quantity 
FROM orders_products op   
INNER JOIN products p
ON op.products_id = p.products_id 
WHERE p.manufacturers_id = 1 AND 
p.orders_id > 10000 

您在product表上同时具有隐式和显式连接(请注意不要再使用隐式连接语法，这是非常不好的programmin做法)，然后看一下代码，我怀疑您正在交叉连接.

YOu had both implicit and explict joins on the products table (Make a note to never again use the implicit join syntax, it is a very bad programmin practice) and looking at the code, I suspect you were getting a cross join.

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